Galactic Thief

About two dozen satellite galaxies orbit the Milky Way, which is a giant among galaxies. By far the brightest of these satellites is the Large Magellanic Cloud, which is best seen from the southern hemisphere. There’s evidence that it owes some of its luster to galactic thievery: It stole some of its stars from another galaxy.

The Large Magellanic Cloud is about 160,000 light-years from Earth, making it one of our nearest galactic neighbors. It’s only about one-tenth as bright as the Milky Way, and just one-hundredth as heavy. It’s easily visible to the unaided eye — but only from south of about Hawaii or southern Mexico.

Astronomers recently observed aging stars in the Large Magellanic Cloud. They found that about five percent of them did not orbit the galaxy’s center with their peers, suggesting the stars came from elsewhere. And the chemical composition of the wayward stars in the Large Magellanic Cloud matches that of the Small Magellanic Cloud, which is the second-largest satellite galaxy to the Milky Way.

The Small Magellanic Cloud is somewhat farther from us than its larger mate, and the two galaxies are just 75,000 light-years apart. That suggests that they’ve been revolving around each other for billions of years. As a result, the astronomers suspect that the Large Magellanic Cloud’s gravity tore millions of stars away from its galactic neighbor — enhancing its own grandeur at the expense of its smaller sibling.

Script by Ken Croswell, Copyright 2013

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